One has to wonder why certain criminals become what they are. I'm not talking about a common thug or a thief here, although one would wonder about them, too. Criminals, who also tend to be victims in many cases, presented in this manga are far more disturbing. In a way though, they may not be disturbing enough, as the real ones may be even worse. Then again, it's not practical to define a standard for such things, so it may all be nothing more than a form of entertainment, both for them and for the readers of this manga.
You be the judge.